FIG. 1 is a schematic diagram illustrating system architecture of System Architecture Evolution (SAE). User Equipment (UE) 101 is a terminal device configured to receive data. Evolved Universal Terrestrial Radio Access Network (E-UTRAN) 102 is a Wireless Access Network (WAN), which includes an e Node B (eNB) configured to provide an interface for UE, to access a wireless network. Mobile Management Entity (MME) 103 is in charge of managing mobile context, session context and safety information of UE. Serving Gateway (SGW) 104 is mainly configured to provide functions of user plane. MME 103 and SGW 104 may be in the same physical entity. Packet Gateway (PGW) 105 is responsible for functions, such as charging, legal monitoring. The PGW 105 and SGW 104 may also in the same physical entity. Policy and Charging Rule Function (PCRF) 106 provides policies of Quality of Service (QoS) and charging guidelines. Serving General Packet Radio Service (GPRS) Supporting Node (SGSN) 108 is a network node device, configured to provide routing for data transmission in Universal Mobile Telecommunications System (UMTS). Home Subscriber Server (HSS) 109 is a home belonging sub-system, which is in charge of protecting user information, such as current position of user device, address of serving node, user safety information, packet data context of user device.
With the improvement about data rate of UE service, operators have offered a new technology. Selected Internet Protocol (IP) Traffic Offload (SIPTO), that is, when accessing a certain specified service, a UE may switch to an Access Point (AP) closer to a WAN, so as to effectively reduce inputted cost of transmission network, and provide better service experience for high data rate.
3rd Generation Partnership Project (3GPP) puts forward that, a network needs to support SIPTO and Local IP Access (LIPA) capabilities. In the SIPTO, when a UE accesses the Internet or other external networks, via Home Evolved Node B (HeNB), Home Node B (HNB) or Macro Base Station, the network may select or re-select a user plane node closer to the WAN for the UE. The LIPA refers to that, a UE accesses a home network or enterprise internal network via the HeNB or HNB. When executing the LIPA, it may also select or re-select a user plane node closer to the HNB, or a user plane node located in an access network of HeNB/HNB for the UE. The user plane node may be a core network device or gateway. Regarding the SAE system, the user plane node may be SGW, or PGW or Local Gateway (LGW). Regarding the UMTS system, the user plane node may be SGSN or Gateway GPRS Supporting Node (GGSN).
FIG. 2 is a schematic diagram illustrating three kinds of system architectures about R11 LIPA. FIG. 2a is a diagram illustrating architecture of a system supporting HeNB evolution. FIG. 2b is a schematic diagram illustrating a system supporting HNB.
An interface between the HeNB/HNB and the LGW is Sxx interface. There may be two possibilities of protocol stack currently supported by the Sxx interface.
The first possibility: the Sxx interface simultaneously supports control plane and user plane protocols, such as GPRS Tunneling Protocol for control plane (GTP-C) and GPRS Tunneling Protocol for User Plane (GTP-U).
The second possibility: the Sxx interface supports user plane protocol, such as GTP-U protocol.
FIG. 2c is a schematic diagram illustrating another network architecture of R11 LIPA. In the architecture, the L-GW is in a tunnel directly connected the HeNB with the MME. There is an Si interface between the L-GW and HeNB. Also, there is the Si interface between the L-GW and the HeNB GW.
FIG. 3 is a flowchart illustrating handover in existed Long Term Evolution (LTE) system. As shown in FIG. 3, the flow mainly includes the following blocks.
Block 301: a source base station determines to hand over.
Block 302: the source base station sends a Handover Request to a source MME, which includes information about target base station, such as target base station ID, target Tracking Area ID (TAI). The Handover Request may also include information, such as target Closed Subscriber Group (CSG) or handover type.
Block 303: the source MME sends a Forward Handover Request to a target MME, which includes information, such as information about target base station obtained from the Handover Request.
Block 304: when the target MME re-selects a SGW for the UE, the target MME executes a session establishment process with the re-selected target SGW.
When it is not necessary to re-select the SGW for the UE, it is not necessary to proceed with block 304.
Block 305: the target MME sends a Handover Request to the target base station.
Block 306: the target base station replies a Handover Request Acknowledge to the target MME.
Block 307: the target MME updates bearing information, according to the target base station about UE handover, which may include the follows. Establish a user plane tunnel between the target base station and the PGW.
When supporting the continuity of LIPA service, in above existed handover process, the following problems are existed, how to establish a user plane between a target base station and L-GW. More specifically, it includes the following problems.
The first problem, for example, when supporting the first architecture of LIPA (the Sxx interface simultaneously supports control plane and user plane protocols), how does the target base station learn to update downlink user plane to HeNB GW/MME or to send a signaling to the L-GW.
The second problem, when supporting the second architecture (the Sxx interface supports the user plane protocol), after receiving uplink and downlink bearer establishment information, the target base station GW may allocate uplink and downlink Tunnel Endpoint Identifier (TEID) and Transport Network Layer (TNL) address for each bearer. Thus, establishment of a direct tunnel between base station and L-GW cannot be guaranteed.
The third problem, when supporting the architecture illustrated in FIG. 2c, how to establish a user plane through the target base station for the UE.
Above descriptions are provided taken Si handover as an example, during X2 handover, the problem about how to establish a direct tunnel between target HeNB and L-GW is also existed.
In the embodiments of the invention, solutions are provided respectively for three kinds of possible architectures.
Currently existed problems are described in the foregoing taken an LTE system as an example. There are the same problems in the UMTS, and more particularly, to whether optimized relocation process is supported during moving of a UE supporting LIPA service. In existed 3G system, optimized relocation process may refer to FIG. 4. As shown in FIG. 4, the process mainly includes the follows.
Block 401: a source HNB sends an RNA Connect or RNA Directly Transfer to a target HNB. The RNA Connect or RNA Directly Transfer includes an enhanced relocation request message about Radio Network Subsystem Application Part (RNSAP) message.
Block 402: the target HNB updates Transport Network Layer (TNL) information about a Radio Access Bearer (RAB) needing relocation. The target HNB sends a Home Node B Application Part (HNBAP) TNL Update Request to a Home Node B Gateway (HNB GW). The HNB GW sends a HNBAP TNL Update Response to the HNBAP.
Block 403: the target HNB sends an RNA Directly Transfer to the source HNB. The RNA Directly Transfer includes an RNSAP Enhanced Relocation Response, which may be used for informing the source HNB that preparation for relocation is successful.
Block 404: the source HNB sends an RNA Directly Transfer to the target HNB, to accept relocation preparations. The RNA Directly Transfer includes an RNSAP Relocation Acceptance, which includes information auxiliary for the relocation process.
Block 405: the source HNB reconfigures the UE to start the relocation process.
Block 406: physical layer synchronization between the UE and target HNB is achieved. The UE has completed a Radio Resource Control (RRC) reconfiguration process. The UE sends a Radio Bearer (RB) Reconfiguration Complete to the target HNB.
Block 407: the target HNB issues an instruction to the HNB GW UE, to indicate that the relocation has been completed successfully. The target HNB sends an HNBAP UE Relocation Complete to the HNB GW. The HNB GW hands over from user plane to target HNB.
Block 408: the HNB GW sends an HNBAP UE De-registration to the source HNB, to indicate successful RNSAP relocation.
Block 409: the source HNB sends an RNA Disconnect to the target HNB, which includes an RNSAP Enhanced Relocation Signaling Transfer, configured to transmit L3 information received by the source HNB during relocation process. The source base station releases resources for the UE.
When the source base station connects with the target base station via an HNB GW with Iurh connection, the RNA message may be routed with the HNB GW.